A rail transit clearance not only defines a rail vehicle and a clearance sectional shape, but also defines an equipment installation position and a reserved space, which therefore is one of the basic guarantees for rail transit safe transportation, and a base for designing rail transit. After the entire rail vehicle is assembled, contour size of the rail vehicle should be detected for determining whether the contour size meets the requirement of the vehicle clearance.
In the conventional technology, the dimension of the vehicle is generally detected by a preset template. However, rail vehicles at least include high speed multiple units, a passenger train, a locomotive, an urban rail vehicle, and etc., which have different clearance standards. Thus, different clearance templates should be manufactured for the detection, thereby the detecting process is slowed down.